20-ton packet is my informal way of refering to a TEU. The container shape and load limits are the physical analogy of the IP packet structure and length limits, hence a network "format". As for the "container port protocol", think of what a multiprotocol IP router does: it takes an IP packet off an ATM network and puts it on an Ethernet network. A container port does the same thing between a ship "network" and a "truck" network. In the case of the container port, the protocol is the set of formal and informal rules about which order to put which TEUs where. My slides are available at http://conferences.oreillynet.com/pub/w/38/presentations.html .